Laminate flooring usually consists of a core of a 6-9 mm fiberboard, a 0.2-0.8 mm thick upper decorative top layer of laminate, preferably comprising sheet material impregnated with thermosetting resins and a 0.1-0.6 mm thick lower balancing layer of laminate, plastic, paper or like material. The top layer provides appearance and durability to the floorboards. The core provides stability, and the balancing layer keeps the board plane when the relative humidity (RH) varies during the year. The floorboards are generally laid floating, i.e., without gluing, on an existing subfloor.
Traditional hard floorboards in floating flooring of this type are usually joined by means of glued tongue and groove joints.
In addition to such traditional floors, floorboards have recently been developed which do not require the use of glue and instead are joined mechanically by means of so-called mechanical joint systems. These systems comprise locking means, which lock the boards horizontally and/or vertically. The mechanical joint systems can be formed by machining of the core of the board. Alternatively, parts of the locking system can be formed of a separate material, which is integrated with the floorboard.
The main advantages of floating floors with mechanical joint systems are that they can easily and quickly be laid with great accuracy. A further advantage of the mechanical joint systems is that the edge portions of the floorboards can be made of materials, which need not have good gluing properties. The edge portions of the floorboard can therefore be impregnated with, for instance, wax, in order to improve the moisture properties.
The most common core material is fiberboard with high density and good stability, usually called HDF—High Density Fiberboard. Other wood fiber based board materials, which could be used are, e.g., MDF (Medium Density Fiberboard), chipboard, plywood and OSB (Oriented Strand Board).
Laminate flooring and also many other floorings with a decorative top layer of plastic, linoleum, wood, veneer, cork and the like are made by the surface layer and the balancing layer being applied to a core material. This application may take place by gluing a previously manufactured decorative layer, for instance when the fiberboard is provided with a decorative high pressure laminate which is made in a separate operation where a plurality of sheets of paper, impregnated with thermosetting resins, are compressed under high pressure and at a high temperature. The currently most common method when making laminate flooring, however, is direct laminating which is based on a more modern principle where both manufacture of the decorative laminate layer and the fastening to the fiberboard take place in one and same manufacturing step. Sheets of paper, impregnated with thermosetting resins, are applied directly to the board and pressed together under pressure and heat without any gluing.
Thick top layers of wood, for instance 1-4 mm, are usually applied to a core consisting of wood blocks whose fiber direction is perpendicular to the fiber direction of the surface layer. Particle board, fiberboard or plywood is also used both when the top layer is thick and also when the top layers are thin veneer with a thickness of, for instance, 0.2-1.0 mm. The top layer of wood is usually protected with one or more layers of oil or varnish. In terms of manufacture it is advantageous if the surface treatment takes place before machining of the edge.
In addition to these methods, a number of other methods are used to provide the core with a surface layer. The core can be painted and varnished. A decorative pattern can be printed on the core surface, which is then, for instance, varnished with a wear layer.
As a rule, the above methods result in a floor element in the form of a large board, which is then sawn into, for instance, some ten floor panels, which are then machined along the edges to floorboards.
The machining of the edges is made in advanced milling machines where the floor panel is positioned between one or more chains and bands mounted in bearings, so that the floor panel can be moved at a high speed and with great accuracy past a number a milling motors, which are provided with diamond cutting tools or metal cutting tools, which machine the edge of the floor panel.
In all these manufacturing methods, the floor panel usually has a top layer when forming its edges by machining.
In recent years it has become more common to provide the above-mentioned floor types with bevels or decorative grooves preferably at the joint edges but also on the surface. These parts are made after providing the floorboard with the decorative top layer. After machining, the edge or decorative grooves must thus as a rule be coated in different manners with, for instance, varnish, paint or the like to achieve the necessary decorative properties and to protect the visible and exposed parts from moisture, dirt and wear. Parts of the joint system that are not visible from the surface are often also coated with property-improving agents, for instance wax, to improve the moisture-resistance and the laying function.